I like the container guy. Been following his videos for a while now. He makes some great bolt on brackets for framing solutions and simplicity.check out the Catainer Guy, he has many you tube video and makes items for containers.
I am not a affiliate of his site, I just found it and found it interesting.
5 Ways To Insulate Your Shipping Container: Which Is The Best?
My brother is insulating his container right now and he went with the flash and bat method. A thin layer of spray insulation then rockwool batts on top of that. It’s a lot more work but makes for a nice sealed insulation envelope with good r value!